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overlord.gaurav
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PostPosted: Sat Oct 17, 2015 2:19 pm    Post subject: Unable to get to GRUB after kernel compilation Reply with quote

Hi all,

This was my first attempt at compiling a kernel. I followed the the Handbook (https://wiki.gentoo.org/wiki/Handbook:AMD64) to compile the kernel.
On reboot I couldn't get to the GRUB and I'm getting the message "Operating System not found"

Here is what my partition table looks lile: http://pastebin.com/tasZjm62
Here is what my /etc/fstab looks like: http://pastebin.com/mvDDcDc3
Here is what my /boot/grub/grub.cfg looks like: http://pastebin.com/b58ZXzgQ

Hoping to get back to Gentoo after I had used it back in 2006 with the Graphical installer.

Thanks and regards.
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charles17
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PostPosted: Sat Oct 17, 2015 3:00 pm    Post subject: Re: Unable to get to GRUB after kernel compilation Reply with quote

According to http://pastebin.com/tasZjm62 your /dev/sda2 is ext4 whereas http://pastebin.com/mvDDcDc3 shows it as ext2.
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overlord.gaurav
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PostPosted: Sat Oct 17, 2015 3:24 pm    Post subject: Re: Unable to get to GRUB after kernel compilation Reply with quote

charles17 wrote:
According to http://pastebin.com/tasZjm62 your /dev/sda2 is ext4 whereas http://pastebin.com/mvDDcDc3 shows it as ext2.


Yes..it is actually supposed to be etx4. Just updating the fstab doesn't seem to fix it..
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charles17
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PostPosted: Sat Oct 17, 2015 3:51 pm    Post subject: Re: Unable to get to GRUB after kernel compilation Reply with quote

overlord.gaurav wrote:
Yes..it is actually supposed to be etx4. Just updating the fstab doesn't seem to fix it..

You'd better reformat /dev/sda2 for ext2 and re-install grub on it and again # grub2-mkconfig -o /boot/grub.grub.cfg while having /boot mounted. See also https://wiki.gentoo.org/wiki/Kernel/Rebuild
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NeddySeagoon
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PostPosted: Sat Oct 17, 2015 4:19 pm    Post subject: Reply with quote

overlord.gaurav,

"Operating System not found" is a message from your BIOS.

Its checking the bootable flag on the MSDOS partition table and finding that its not set correctly.
If you have installed using GPT, you still have a MSDOS partition table and your BIOS still checks it.

fdisk -t dos /dev/...

will let you set the bootable flag - do not do anything else there.
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Computer users fall into two groups:-
those that do backups
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overlord.gaurav
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PostPosted: Sat Oct 17, 2015 6:56 pm    Post subject: Re: Unable to get to GRUB after kernel compilation Reply with quote

charles17 wrote:
overlord.gaurav wrote:
Yes..it is actually supposed to be etx4. Just updating the fstab doesn't seem to fix it..

You'd better reformat /dev/sda2 for ext2 and re-install grub on it and again # grub2-mkconfig -o /boot/grub.grub.cfg while having /boot mounted. See also https://wiki.gentoo.org/wiki/Kernel/Rebuild


That didn't fix the issue either..

NeddySeagoon wrote:

overlord.gaurav,

"Operating System not found" is a message from your BIOS.

Its checking the bootable flag on the MSDOS partition table and finding that its not set correctly.
If you have installed using GPT, you still have a MSDOS partition table and your BIOS still checks it.

fdisk -t dos /dev/...

will let you set the bootable flag - do not do anything else there.


I don't exactly know how to set the bootable flag. The output of 'print' after your command is this: http://pastebin.com/jwYYZqmE
While speaking on the IRC channel I was suggested that I set the bootable flag because of the protective MBR state or something.
So, my current partition table appears like this (http://pastebin.com/8vM2n0Le) on parted.
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NeddySeagoon
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PostPosted: Sat Oct 17, 2015 7:12 pm    Post subject: Reply with quote

overlord.gaurav,

This is the protective MSDOS partition table.
Code:
Device    Boot Start       End    Blocks  Id System
/dev/sda1 *        1 976773167 488386583+ ee GPT

It shows that the bootable flag is set. As long as you saved your change, you are good.

Has your error message changed any?
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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overlord.gaurav
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PostPosted: Sat Oct 17, 2015 7:23 pm    Post subject: Reply with quote

NeddySeagoon wrote:
overlord.gaurav,

This is the protective MSDOS partition table.
Code:
Device    Boot Start       End    Blocks  Id System
/dev/sda1 *        1 976773167 488386583+ ee GPT

It shows that the bootable flag is set. As long as you saved your change, you are good.

Has your error message changed any?


Nope. Still no luck :cry:
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NeddySeagoon
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PostPosted: Sat Oct 17, 2015 7:30 pm    Post subject: Reply with quote

overlord.gaurav

How many HDD do you nave connected?
Count USB sticks too.

I suspect the BIOS is not set to boot from /dev/sda.
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NeddySeagoon

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those that do backups
those that have never had a hard drive fail.
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overlord.gaurav
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PostPosted: Sat Oct 17, 2015 7:36 pm    Post subject: Reply with quote

NeddySeagoon wrote:
overlord.gaurav

How many HDD do you nave connected?
Count USB sticks too.

I suspect the BIOS is not set to boot from /dev/sda.


2 HDDs - One internal hard disk at /dev/sda
And the other one is a USB stick from which I boot up the live session of Gentoo.
I remove the USB stick while trying to get the GRUB
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NeddySeagoon
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PostPosted: Sat Oct 17, 2015 7:45 pm    Post subject: Reply with quote

overlord.gaurav,

Post your
Code:
fdisk -l -t dos /dev/sda
again.
Thats a lower case L for list, not a numeral 1.

Ping me in #gentoo if you want
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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overlord.gaurav
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PostPosted: Sat Oct 17, 2015 8:49 pm    Post subject: Reply with quote

NeddySeagoon wrote:
overlord.gaurav,

Post your
Code:
fdisk -l -t dos /dev/sda
again.
Thats a lower case L for list, not a numeral 1.

Ping me in #gentoo if you want


UPDATE
As per my conversation with NeddySeagoon on #Gentoo,
Here's how I got past the "No OS found" error and got the BIOS to detect the GRUB and get an error message like:
Code:
GRUB loading. Welcome to grub error: no such partition


I am running on a Dell Inspiron 14R-N4110. The system seems to check the partition type for booting.

fdisk -l -t msdos
Code:

gentoo@livecd ~ $ sudo fdisk -l -t dos
 
Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x00000000
Partition 1 does not start on physical sector boundary.
 
Device    Boot Start       End    Blocks  Id System
/dev/sda1 *        1 976773167 488386583+ ee GPT
 
 
Disk /dev/sdb: 7.5 GiB, 8004304896 bytes, 15633408 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x133381df
 
Device    Boot     Start       End  Blocks  Id System
/dev/sdb1 *            0   5783399 2891700   0 Empty
/dev/sdb2            304     16687    8192  ef EFI (FAT-12/16/32)
/dev/sdb3          16688     82222   32767+  0 Empty
 
 
Disk /dev/sdb1: 2.8 GiB, 2961100800 bytes, 5783400 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x133381df
 
Device      Boot     Start       End  Blocks  Id System
/dev/sdb1p1 *            0   5783399 2891700   0 Empty
/dev/sdb1p2            304     16687    8192  ef EFI (FAT-12/16/32)
/dev/sdb1p3          16688     82222   32767+  0 Empty


So, we changed the partition type of /dev/sda from ee to 7, ie. from GPT to HPFS/NTFS/exFAT
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